Monthly Archives: December 2015

Death to Fast Plants

I quite like browsing the WordPress stats for Biological Burblings. At the time of writing, the blog has had visitors from 55 countries, with over 1000 different visitors in total making up the 2798 views.


It’s important to stay grounded, so only 8 likes (that’s a like every 372 views – thanks, guys….) and the fact that just 7 countries get into double figures for viewing is a striking contrast to, say, Zoe Sugg’s Zoella vlog that has had over 540 million visits since it started. I’m obviously in the wrong business.

I’m also deeply intrigued by the single figure visits from, say, Russia. Who was this person? What word/phrase did they put into their search engine? How disappointed were they when they ended up here?

Anyway, this is the last burble of 2015 as I’m now just 2 days from the 3 week Xmas holiday. I’m going to stick with my KS3 project, only this time I’m going to talk about something I tried with Year 8, as it absolutely captures what I think science teaching should be about.

The topic was Hydrogen, Metals and Acids. To be honest, I hadn’t changed much. The students really enjoy the Chemistry topics and apart from updating the resources and trying to make the lessons a bit pacier and a bit more investigative and a lot less note-takey, I had pretty much stuck to the script. But the final lesson was, I felt, a bit dry. They had to neutralise a base – ammonium hydroxide -with hydrochloric acid and then produce a purifed sample of the resulting salt, ammonium chloride.

All well and good. Lots of useful skills to develop here and they were conscientious and focussed and all ended up with small samples of a white powder in their evaporating basins. But the activity was titled “Making a Fertiliser”. This seems to be some GCSE legacy topic, an attempt to make neutralisation relevant and important. But it stopped there. The students were meant to look at their white solid and go, “aha! I’ve made a fertiliser!” And that was it.

But surely the obvious thing to do is actually try it out? It’s meant to be a fertiliser – so, what are fertilisers meant to do? Let’s see if it works!

I showed them the brilliant SAPS fast plant kits and asked them to design an experiment. They did this effortlessly, establishing the need for a control and then adding varying quantities of ammonium chloride to the 3 remaining cells. Two rapid cycling brassica seeds in each cell and they were tucked away under the home made lightbank….


home-made light bank – note brine shrimp tank, brine shrimp bottles, fly breeding bottles, fast plants, and general sense of complete untidiness….

There’s a reason they’re called Fast Plants. Planted on Friday, they had germinated by the following Wednesday and I was able to show the class their results. Their reaction was superb. At first, they assumed they had labelled their pots incorrectly. Because the pattern was exactly the opposite of what they had expected to happen.  In other words, the control, the cell with no ammonium chloride at all, had grown the most. The vast majority of cells with ammonium chloride hadn’t even germinated, and those that had showed significantly less growth. Check it out!


It was a glorious “that’s funny….” moment, where their assumptions and preconceptions were completely overturned. Perhaps it doesn’t sound much written down, but the look on their faces was priceless.

The result was consistent across all ten groups, so we could talk about the value of repeats, but the real learning came from the interpretation. Why did you think it would make them grow? Because you told us it would! Because the activity was “Making a fertiliser!” You lied to us! You killed our babies!

I reminded them that I, too, had no idea what would happen. They had tested an idea through experiment and discovered something completely new and unexpected. It’s called Science.

So we talked about why we might expect an Ammonium salt to work as a fertiliser – I showed them molymods of Ammonium and an amino acid, and got them to identify the atoms. Where can you get carbon, hydrogen and oxygen from? Yes, exactly, water and carbon dioxide. But what else is in amino acid? They see the common atom, the nitrogen.

So why didn’t it work? I encourage them to throw out testable ideas. Perhaps the chloride bit is toxic? Perhaps it fertilises in tiny amounts and poisons in higher concentrations?

This year it was a casual add on to the end of the topic that I thought might be quite fun. Next year, I’m going to build an investigation around it. Perhaps they could produce different ammonium salts with different acids and compare the effects? Perhaps they could look at this idea of really small concentrations? And so on.

Right, I’m done. Thanks for following the blog. I hope you all have a wonderful holiday. Next year, among other things, I plan to answer a questions posed by my old PGCE colleague Ruth in the comments section, on how I’ve managed to stay so enthusiastic. I must admit it’s worn a little thin in recent months, but I’ll see what I can do! And one of my SMART targets for next year is to get my “Likes” into double figures…. Go on, do your bit!

Back in 2016

Shopping in a parallel universe

So this is quite fun.

As I’ve mentioned before, my big project for last year and this has been to completely re-write the KS3 SoWs and lesson plans for the whole of Science. I wanted to completely change the emphasis of the subject, from one of students receiving information, writing it down and regurgitating it on demand, to a course based on investigative practical work with as little note taking as possible.

The main challenge for me has been the Physics topics. Biology is obviously not a problem, and Chemistry was my favorite A-level, but I dropped Physics at 14, baffled and frustrated by moments, magnetism and the apparent pointlessness of Hooke’s Law.

But conceptual difficulty for a teacher can be a good thing. If I don’t understand something, I certainly can’t teach it effectively. If I have to go out and learn something new, then it’s much easier for me to understand how and why a student might struggle with it. And it forces me to come up with imaginative solutions.

So one of the topics that the Head of Physics wanted covered was Energy. I did lots of reading for this. The most helpful resources were the Nuffield Physics website which provided lots of excellent ideas for practical work (check out what you can do with a brick!) and Peter Atkin’s superb 4 Laws that Drive the Universe….


which I found absolutely compelling.

So, I put together a course that focused on the idea of Energy as always being in a store, and that to make anything happen, energy has to move from one store to another (Nuffield recommends that you make no mention of types  of energy as this leads to unhelpful confusion). So the students burned wood shavings to compare the quantity of energy in different types of wood and built splendid (and occasionally terrifying) trebuchets to illustrate the idea of energy transfer.

And then there was this idea for a lesson on Entropy.

I started with the traditional idea of comparing Energy to Money. You can keep them both in a “store”. But nothing happens until you move it from one store to another. Plus it’s quantifiable. When they were happy with that, we moved on to the activity.

You need several boxes of maltesers, a paper shredder and wads of pretend money – £100 in £10 notes, and £200 in £20 notes.

Divide the class up. For a class of 20, 5 shopkeepers. Tell them they’re selling boxes of maltesers for the princely sum of £100 a box. They cannot pass over a box until they have the full £100 in their hands.

5 groups of 2 shoppers each. Give them a wad of £100 each. Tell them that their challenge is to buy a box of maltesers.

And 5 intermediates. Make it very clear to everyone that money must pass through the intermediates. So if shoppers want to buy something, they must pass the money to the intermediate who will pass it on to the shopkeeper.

Then take the intermediates somewhere quiet and explain that when the shoppers give them some money, they must put 90% of it into the shredder and only give 10% to the shopkeeper. But they mustn’t tell anyone what they’re going to do!

Then let the game commence.

It is joyous. Excited by the prospect of chocolate, the shoppers eagerly hand over their £100 wad to an intermediate. The look of shock and outrage on their faces when the intermediates calmly shred £90 is utterly priceless. Nobody gets any chocolate. What’s going on?

So I ask them to imagine this weird parallel universe where shopping involves the automatic shredding of 90% of their money. To buy something worth £10, they have to hand over £100. Where’s the other £90? They point – it’s in the shredder! In other words, it’s still in the universe, it hasn’t been used up, it’s just no longer in a usable form.

So I restart the game. This time the shoppers have wads of £200. Can they figure out a stratagem for getting any maltesers? Perhaps they need to think collectively?

Eventually they get it. If they pool their money, they can hand over £1000 to an intermediate and although £900 gets shredded, a shopkeeper will get £100 and the class can all have a malteser each.

But how does this link to energy? I produce some alcohol and ask them to imagine it’s petrol. How do I transfer the energy? It needs to burn. So I pour some into a crucible and light it. If this is a car, I ask, where do I want to move the energy to? The wheels. But feel it! What is happening to most of the energy? They can feel the heat.

For shredded money, read heat. We’re looking at Entropy.

This leads neatly to an exercise in trying to light a fire with a fire drill, which generates lots of smoke but, not yet at least, any flames…. But when we go through the various energy transfers and the first concept of some kind of Sankey diagram, it’s quite fun to ask them how they feel. Hot? Well, why would that be….

Last burble of the year next week…..